Methods for refurbishing aerospace components

Abstract

Methods for refurbishing aerospace components by removing corrosion and depositing protective coatings are provided herein. In one or more embodiments, a method of refurbishing an aerospace component includes exposing the aerospace component containing corrosion to an aqueous cleaning solution. The aerospace component contains a nickel superalloy, an aluminide layer disposed on the nickel superalloy, and an aluminum oxide layer disposed on the aluminide layer. The method includes removing the corrosion from a portion of the aluminum oxide layer with the aqueous cleaning solution to reveal the aluminum oxide layer, then exposing the aluminum oxide layer to a post-rinse, and forming a protective coating on the aluminum oxide layer.

What is claimed is: 
     
       1. A method of refurbishing an aerospace component, comprising:
 exposing an aerospace component containing corrosion to an aqueous cleaning solution, wherein the aerospace component comprises a nickel superalloy, an aluminide layer disposed on the nickel superalloy, and an aluminum oxide layer disposed on the aluminide layer, and wherein the corrosion is contained on a first portion of the aluminum oxide layer while a second portion of the aluminum oxide layer is free of the corrosion; 
 removing the corrosion from the first portion of the aluminum oxide layer with the aqueous cleaning solution to reveal the first portion of the aluminum oxide layer; then 
 exposing the first and second portions of the aluminum oxide layer to a post-rinse; and 
 forming a protective coating on the first and second portions of the aluminum oxide layer. 
 
     
     
       2. The method of  claim 1 , wherein the aqueous cleaning solution comprises water, a complexing agent, and a base. 
     
     
       3. The method of  claim 2 , wherein the complexing agent comprises ethylenediaminetetraacetic acid (EDTA) and/or a salt thereof, and wherein the base comprises a hydroxide. 
     
     
       4. The method of  claim 2 , further comprising:
 exposing the aerospace component to the aqueous cleaning solution for about 1 hour to about 5 hours; 
 sonicating the aerospace component in the aqueous cleaning solution; and 
 maintaining the aqueous cleaning solution at a temperature of about 20° C. to about 50° C. 
 
     
     
       5. The method of  claim 1 , wherein prior to exposing the aerospace component to the aqueous cleaning solution, the method further comprises:
 exposing the aerospace component to a pre-rinse comprising an organic solvent and water for about 5 minutes to about 60 minutes; 
 sonicating the aerospace component in the pre-rinse; and 
 maintaining the pre-rinse at a temperature of about 20° C. to about 50° C. 
 
     
     
       6. The method of  claim 1 , further comprising:
 exposing the first and second portions of the aluminum oxide layer to the post-rinse for about 5 minutes to about 60 minutes; 
 sonicating the aerospace component in the post-rinse; and 
 maintaining the post-rinse at a temperature of about 20° C. to about 50° C. 
 
     
     
       7. The method of  claim 1 , wherein the aluminide layer comprises nickel aluminide, titanium aluminide, magnesium aluminide, iron aluminide, or combinations thereof. 
     
     
       8. The method of  claim 1 , wherein the aluminide layer has a thickness of about 20 μm to about 500 μm, wherein the aluminum oxide has a thickness of about 1 μm to about 50 μm, and wherein the aerospace component has a thickness of about 1 mm to about 5 mm. 
     
     
       9. The method of  claim 1 , wherein the protective coating is deposited by a vapor deposition process, wherein the protective coating comprises chromium oxide, aluminum oxide, aluminum nitride, hafnium oxide, titanium oxide, titanium nitride, tantalum oxide, tantalum nitride, dopants thereof, or any combination thereof, and wherein the protective coating has a thickness of about 1 nm to about 10,000 nm. 
     
     
       10. A method of refurbishing an aerospace component, comprising:
 exposing an aerospace component containing corrosion to an acidic cleaning solution, wherein the aerospace component comprises a nickel superalloy, an aluminide layer disposed on the nickel superalloy, and an aluminum oxide layer disposed on the aluminide layer, and wherein the corrosion is contained on and within the aluminum oxide layer; 
 removing the corrosion and the aluminum oxide layer with the acidic cleaning solution to reveal the aluminide layer; then 
 exposing the aluminide layer to a post-rinse; and 
 forming a protective coating on the aluminide layer. 
 
     
     
       11. The method of  claim 10 , wherein the acidic cleaning solution comprises water and about 10 volume percent (vol %) to about 40 vol % of sulfuric acid. 
     
     
       12. The method of  claim 11 , further comprising:
 exposing the aerospace component to the acidic cleaning solution for about 30 minutes to about 90 minutes; 
 stirring the acidic cleaning solution while exposing the aerospace component; and 
 maintaining the acidic cleaning solution at a temperature of about 50° C. to about 150° C. 
 
     
     
       13. The method of  claim 10 , wherein prior to exposing the aerospace component to the acidic cleaning solution, the method further comprises:
 exposing the aerospace component to a pre-rinse for about 5 minutes to about 60 minutes; 
 sonicating the aerospace component in the pre-rinse; and 
 maintaining the pre-rinse at a temperature of about 20° C. to about 50° C. 
 
     
     
       14. The method of  claim 10 , wherein prior to exposing the aerospace component to the acidic cleaning solution, the method further comprises:
 exposing the aerospace component to an aqueous cleaning solution for about 1 hour to about 5 hours; 
 sonicating the aerospace component in the aqueous cleaning solution; and 
 maintaining the aqueous cleaning solution at a temperature of about 20° C. to about 50° C. 
 
     
     
       15. The method of  claim 14 , wherein the aqueous cleaning solution comprises water, a complexing agent, and a base, wherein the complexing agent comprises ethylenediaminetetraacetic acid (EDTA) and/or a salt thereof, and wherein the base comprises a hydroxide. 
     
     
       16. The method of  claim 10 , wherein subsequent to exposing the aerospace component to the acidic cleaning solution, the method further comprises:
 exposing the aluminide layer to an aqueous cleaning solution for about 1 hour to about 5 hours; 
 sonicating the aerospace component in the aqueous cleaning solution; and 
 maintaining the aqueous cleaning solution at a temperature of about 20° C. to about 50° C. 
 
     
     
       17. The method of  claim 10 , further comprising:
 exposing the aluminide layer to the post-rinse for about 10 minutes to about 90 minutes; 
 sonicating the aerospace component in the post-rinse; and 
 maintaining the post-rinse at a temperature of about 20° C. to about 50° C. 
 
     
     
       18. The method of  claim 10 , wherein the aluminide layer comprises nickel aluminide, titanium aluminide, magnesium aluminide, iron aluminide, or combinations thereof, and wherein the aluminide layer has a thickness of about 20 μm to about 500 μm, and wherein the aluminum oxide has a thickness of about 1 μm to about 50 μm. 
     
     
       19. The method of  claim 10 , wherein the protective coating is deposited by a vapor deposition process, wherein the protective coating comprises chromium oxide, aluminum oxide, aluminum nitride, hafnium oxide, titanium oxide, titanium nitride, tantalum oxide, tantalum nitride, dopants thereof, or any combination thereof, and wherein the protective coating has a thickness of about 1 nm to about 10,000 nm. 
     
     
       20. A method of refurbishing an aerospace component, comprising:
 exposing an aerospace component containing corrosion to an acidic cleaning solution, wherein the aerospace component comprises a nickel superalloy, an aluminide layer disposed on the nickel superalloy, and an aluminum oxide layer disposed on the aluminide layer, and wherein the corrosion is contained on the aluminum oxide layer and within the aluminum oxide layer and a first portion of the aluminide layer; 
 removing the corrosion, the aluminum oxide layer, and the first portion of the aluminide layer with the acidic cleaning solution to reveal a second portion of the aluminide layer; then 
 exposing the aerospace component to a post-rinse; and 
 forming a protective coating by a vapor deposition process on the second portion of the aluminide layer, wherein the vapor deposition process is a thermal atomic layer deposition (ALD) process, a plasma-enhanced ALD (PE-ALD) process, a thermal chemical vapor deposition (CVD) process, a plasma-enhanced CVD (PE-CVD) process, or a pulsed-CVD process.